Deployable flap edge fence

ABSTRACT

A method and systems are disclosed for reducing fluid flow noise. The method and systems use a thermal mechanism to deploy a flap edge fence during landing and/or other operating conditions, and stow the flap edge fence during other operational conditions such as cruise. The flap edge fence is controlled passively by ambient temperature or actively by a controller based on temperature changes corresponding to various operating conditions.

TECHNICAL FIELD

Embodiments of the present disclosure relate generally to reducing noiseproduced by fluid dynamic surfaces moving in a fluid. More particularly,embodiments of the present disclosure relate to a deployable flap edgefence for an aircraft for reducing airflow noise (aerosound) produced bya flap edge when it is exposed to the fluid (e.g. air) during certainflight conditions.

BACKGROUND

An airplane's airframe and engines produce varying amounts ofobjectionable audible noise during different flight conditions. Duringdeparture, the engines produce most of the noise; however, duringapproach, airframe noise is a much greater factor. Airframe noise isgenerated by air flowing over the airplane's fuselage, landing gear,wing leading and trailing edges equipped with high-lift devices and flapsystems. On the approach to landing, high lift systems, such as wingleading edge devices and wing trailing edge flap systems, are extendedand the engines are operated at low thrust levels. Accordingly, the mostaudible noise produced by flap systems occurs on approach when the flapsare extended and lateral flap edges are exposed. Furthermore, recentadvances in technology have reduced engine noise significantly duringall flight conditions. Therefore, airframe noise has become a moredominant source of aerosound, and particularly so for an airplane duringapproach to landing.

One of the main noise-generating mechanisms at play in flap edge flowscan be attributed to shear layer fluctuations and their interaction withsurrounding edges and surfaces. When an airfoil creates lift, theinherent pressure differences between the top and bottom surfaces causeair to leak around the edges of the airfoil in an attempt to equalizethe pressure. Since flap edges are usually sharp, this results in aseparated shear layer emanating from the bottom side of the airfoil.Similarly another vortex emerges from the sharp junction between theside edge 108 and the upper surface of the flap 110. As shown in FIG. 1,this occurs throughout the chordlength 102, and the shear layer rolls up(reference number 104 represents this roll up effect) into a vortex core106 which is transported downstream. These two vortex systems ditheraround the surrounding surfaces, emitting broadband noise. At someangle-of-attack dependent chord-wise location, the lower vortex corewill spill over the sharp top surface edge 108 creating additionalbroadband noise.

After spilling over the sharp edge 108, the lower surface vortex coreinteracts with the upper surface vortex. As shown in FIG. 2, the twovortex-systems then entrain each other and develop into a high-intensitytightly formed vortex core 214 which can be detrimental for airplanescrossing the wake further downstream

In the past, various approaches have been taken to attenuate thevortices produced by flaps and other lifting surfaces. Flap edge fenceshave been proposed as a way to mitigate the noise source emerging fromthe flap edges. As will be explained in more detail below, a generalflap edge fence (not shown in FIG. 2) forms a barrier that modifies anddisplaces the flap tip vortex system 214 leaving the flap edge 208.

One of the problems facing the successful installation of such a flapedge fence is that, while highly beneficial with a fully extended flapsystem, the fences are far from optimal in high-speed cruise conditions.Mounted perpendicularly to the deployed flap trailing edge, the fencemay form a significant angle to the local air-flow when the flap isstowed due to flap Fowler motion and inherent cross flow of anythree-dimensional wing. This would result in wasted lifting forces andadditional drag, which in turn creates unnecessary loads on thestructure. Any such additional drag in cruise should be kept to aminimum for efficient operation. Currently, existing flap edge fencesare fixed and no alternatives are available.

To minimize aerosound due to the extension of flaps during aircraftoperations and, more specifically, to reduce drag during high-speedcruise conditions, it is desirable to have a deployable flap edge fenceso that any additional drag in cruise is kept to a minimum for efficientoperation. Other desirable features and characteristics of embodimentsof the present invention will become apparent from the subsequentdetailed description and the appended claims, taken in conjunction withthe accompanying drawings and the foregoing technical field andbackground.

BRIEF SUMMARY

A method and systems for reducing fluid flow noise using a deployableflap edge fence are proposed. The method shapes the deployable flap edgefence in response to a temperature change. In this regard, the methodreduces airflow noise by thermally activating a deployable flap edgefence for approach and landing. With the flap edge fence deployed,vortices generated at the side edge of a flap are prevented fromdirectly rolling over from the lower surface of the flap to the uppersurface of the flap. The method also reduces drag by stowing thedeployable flap edge fence for cruise thereby reducing interaction ofthe deployable flap edge fence with local air-flow over the body.

A first embodiment includes: a flap coupled to a wing main element and areconfigurable flap edge fence coupled to the flap. A control mechanismdeploys the flap edge fence for a first set of flight conditions (e.g.approach and landing), and stows the flap edge fence for a second set offlight conditions (e.g. cruise) in response to a temperature change.

A second embodiment employs a trained shaped memory alloy (SMA) torquetube to thermally stow or deploy the reconfigurable flap edge fence. Inthis regard, the second embodiment includes: a flap coupled to the wingmain element, a flap edge fence coupled to the flap, a trained SMAtorque tube coupled to the flap edge fence and the flap, and configuredto position (deploy, or stow away) the flap edge fence in response to atemperature change. A controller is coupled to the trained SMA torquetube to thermally activate the trained SMA torque tube at occurrence ofa first temperature range (corresponding to approach and landingaltitudes). The thermal activation drives the SMA torque tube towards anaustenitic trained shape thereby generating a moment between the flapedge fence and the flap with sufficient torque to deploy the flap edgefence. The SMA torque tube deactivates at a second temperature range(corresponding to cruise altitudes) by returning to its martensiticshape which produces a torque moment that stows the reconfigurable flapedge fence onto the flap for cruise. In this regard, the controllermonitors the temperature of the SMA torque tube and provides thetemperature change by heating/cooling of the SMA torque tube as neededbased on a flight condition. Alternatively, thermal activation can alsobe passively provided by ambient temperature corresponding to analtitude at the flight condition.

A third embodiment uses a bending flexure flap edge fence made from SMAmaterial to thermally deploy, stow away, or change orientation to alignwith the flow. In this regard, the third embodiment includes: a flapcoupled to the wing main element, and an SMA reconfigurable/deployableflap edge fence coupled to the flap and configured to deploy and stow inresponse to temperature change. This adaptation is accomplished bythermally deploying the SMA flap edge fence to a predetermined bendingangle for a first set of flight conditions, and thermally stowing theSMA flap edge fence along the streamlines of the local air flow for asecond set of flight conditions. The thermal condition may be providedactively by a controller (using aircraft systems), or alternatively, thetemperature change may be provided passively by changes in ambienttemperature.

A further embodiment includes an adaptive fluid dynamic system forreducing drag/fluid noise due to fluid flow. The system includes: a bodycapable of generating lift by moving through a fluid, and a deployablebody edge fence coupled to the body. A control mechanism is used toreconfigure the body edge fence into a deployed state for a first set ofoperating conditions, and to reconfigure the body edge fence again intoa stowed state for a second set of operating conditions.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of embodiments of the present disclosuremay be derived by referring to the detailed description and claims whenconsidered in conjunction with the following figures, wherein likereference numbers refer to similar elements throughout the figures.

FIG. 1 is an existing art diagram that illustrates a shear layeremanating around a sharp flap edge and which evolves into a vortex core;

FIG. 2 is an existing art illustrating a schematic top plan view of partof a wing showing lower and upper surface vortex cores entraining eachother to form a high-intensity vortex core;

FIG. 3 is an existing art illustrating a top view of a portion of anaircraft wing showing a plurality of flaps and slats to which aplurality of deployable flap edge fences may be mounted;

FIG. 4 is a perspective top view of a system for reducing airflow noisefor an aircraft showing a relatively small flap edge fence mounted anddeployed on the suction side of a flap;

FIG. 5 is a perspective top view of a system for reducing airflow noisefor an aircraft showing a relatively large size flap edge fence mountedand deployed on the suction side of a flap;

FIG. 6 is a perspective bottom view of a system for reducing airflownoise for an aircraft, showing another flap edge fence mounted anddeployed on the pressure side of a flap;

FIG. 7 is a perspective view that illustrates a flap edge fence modelstowed via an SMA torque tube employing a controller;

FIG. 8 is a perspective view that illustrates a flap edge fence modeldeployed via an SMA torque tube;

FIG. 9 is a side view that illustrates an SMA torque tube;

FIG. 10 is a perspective view that illustrates a deployed SMA flap edgefence model;

FIG. 11 is a perspective view that illustrates an SMA flap edge fencemodel that is stowed along the direction of the streamlined air flow;and

FIG. 12 is a flow chart illustrating a process for reducing airflownoise using temperature changes to operate a deployable flap edge fence.

DETAILED DESCRIPTION

The following detailed description is merely illustrative in nature andis not intended to limit the embodiments of the disclosure nor theapplication and uses of such embodiments. Furthermore, there is nointention to be bound by any expressed or implied theory presented inthe preceding technical field, background, brief summary or thefollowing detailed description.

Embodiments of the disclosure may be described herein in terms offunctional and/or logical block components and various processing steps.It should be appreciated that such block components may be realized byany number of hardware, software, and/or firmware components configuredto perform the specified functions. For the sake of brevity,conventional techniques and components related to signal processing,aircraft control systems, high lift devices, and other functionalaspects of the systems (and the individual operating components of thesystems) may not be described in detail herein. In addition, thoseskilled in the art will appreciate that embodiments of the presentdisclosure may be practiced in conjunction with a variety of differentaircraft control systems and aircraft wing configurations, and that thesystem described herein is merely one example embodiment of thedisclosure.

The following description refers to elements or nodes or features being“connected” or “coupled” together. As used herein, unless expresslystated otherwise, “connected” means that one element/node/feature isdirectly joined to (or directly communicates with) anotherelement/node/feature, and not necessarily mechanically. Likewise, unlessexpressly stated otherwise, “coupled” means that oneelement/node/feature is directly or indirectly joined to (or directly orindirectly communicates with) another element/node/feature, and notnecessarily mechanically. Thus, although FIGS. 4-11 depict examplearrangements of elements, additional intervening elements, devices,features, or components may be present in an embodiment of thedisclosure.

A wing is a surface used to produce lift and therefore flight, fortravel in air or another medium. An example of an application in anothermedium is a hydrofoil wing in water. The wing sectional shape is usuallyan airfoil with a large lift-to-drag ratio. A common use for a wing isin flight, using forward motion to create vertical lift, but wings arealso used to produce downward force holding racing cars on the ground.Furthermore, a sail boat moves by using sails and a keel like a verticalwing to produce lift in the horizontal plane. In this regard, althoughexample embodiments described herein are in terms of the common use inflight, the embodiments of the disclosures are also applicable, withoutlimitation, to a body capable of generating lift by moving through afluid, as utilized in sail boats, hydrofoils, racing cars and the like.

FIG. 3 is an existing art illustration showing a schematic top view ofan aircraft wing 300 having a wing main element 302, a plurality offlaps 304, and leading edge devices 306 (e.g., slats). For thisembodiment, a plurality of deployable flap edge fences may be mounted onthe flaps 304 or the leading edge devices 306. Details of deployablefences and how they relate to other aerodynamic surfaces are not shownin FIG. 3.

Flaps 304 are aerodynamic surfaces attached to the trailing edge of thewing main element 302. When deployed, the flaps 304 increase the lift(and drag) of the wing main element 302. Depending on the aircraft type,configuration and method of takeoff (e.g., short field, soft field,normal, etc.), flaps 304 are often partially extended for take-off togive the aircraft more lift when trying to leave the ground. Duringlanding, the flaps 304 are usually fully extended to allow the aircraftto fly slower (by increasing the lift generated by the wings at lowspeeds) and to steepen the approach to the landing site. Significantairframe noise would be generated by the flap edges unless they arefitted with fences or any other successfully implemented noisemitigation device.

Slats 306 are aerodynamic surfaces attached to the leading edge of thewing main element 302, which, when deployed, allow the wing main element302 to operate at a higher angle of attack. By deploying slats 306, theangle of attack at which stall occurs is increased. Slats 306 areusually used while landing or performing maneuvers which take theaircraft close to stall, but are usually retracted in normal flight tominimize drag. For example, during takeoff, the slats 306 are partiallyextended to provide attached flow over the wing main element 302 at highangles of attack. Shortly after take-off the slats 306 would beretracted to improve the lift-to-drag ratio of the climboutconfiguration. Similar to flaps 304, when slats 306 are fully/partiallyextended, aerodynamic noise could be generated at the slat without thepresence of slat edge fences or another successfully implemented noisemitigation device.

FIG. 4 is a perspective top view of an example embodiment of a system400, for reducing airflow noise for an aircraft. In the exampleembodiment shown in FIG. 4, the system 400 may include, withoutlimitation: a wing main element 402, a flap 408 coupled to the wing mainelement 402, a deployable flap edge fence 406 coupled to the flap 408,and a control mechanism 416.

Wing main element 402 is the main part of an aircraft wing as explainedin FIG. 3 above. Wing main element 402 includes a trailing edge 404 anda leading edge (not shown in FIG. 4). The flap 408 is usually coupled tothe trailing edge 404.

Flap 408 includes a leading edge 410, a trailing edge 412, a tip 414, anupper surface 418 and a lower surface (not shown in FIG. 4). The flap408 is a moveable surface mounted on the trailing edge 404 of the wingmain element 402. As shown in FIG. 4, the flap 408 is deflected down toincrease the effective curvature of the wing 300 (see FIG. 3), toproduce additional lift, and to reduce the stalling speed of the wing300. Flap 408 is used during low speed, high angle of attack flightslike descent for landing.

Flap edge fence 406 is suitably configured to form a barrier that closes(or significantly closes) the gap (not shown in FIG. 4) between the wingmain element 402 and the flap 408. In the example embodiment of FIG. 4,the flap edge fence 406 has an upper contour 420, a lower contour 422, athickness 424, and a length 426, and the flap edge fence 406 is mounted(perpendicularly when deployed) on the suction side 418 (top surface) ofthe flap 408. For this embodiment, the lower contour 422 is attachedchordwise to the tip 414 of the flap 408, and the upper contour 420 issubstantially parallel to the flap 408 and matches the contour of theflap 408. The length 426 may extend from the leading edge 410 to thetrailing edge 412 of flap 408. The upper contour 420, lower contour 422,thickness 424, and length 426 can vary according to variousconsiderations, for instance, the type of high-lift device such as thewing 200 and the gap between the wing main element 402 and the flap 408.The flap edge fence 406 may be secured to the tip 414 of the flap 408 byany suitable technique or technology, for example, the flap edge fence406 may be riveted, welded, or bolted chordwise to tip 414 of the flap408. While the flap edge fence 406 is described as being mountedperpendicularly (when deployed), various other configurations may alsobe used, for example, a configuration that is canted outward from thevertical to conform with air flow.

Although FIG. 4 shows a relatively small flap edge fence 406, generallythe flap edge fence 406 may have, without limitation, the same sizeand/or aerodynamic shape as the flap 408, a flat thin plate, or the likethat is suitable for stowing and deployment according to embodiments ofthis disclosure. This facilitates closing of the gap between the wingmain element 402 and the flap 408. For example, as shown in FIG. 5, arelatively large deployable flap edge fence 502 as compared to flap edgefence 406 may be mounted on the suction side 506 (upper surface) of theflap 504.

Alternatively or additionally, the deployable flap edge fences may bemounted on the flap lower surface (pressure side) of the flap. Forexample, as shown in FIG. 6, a reconfigurable flap edge fence 602 may bemounted on the pressure side 606 (lower surface) of the flap 604. Flapedge fences may also be mounted on both lower and upper surfaces of theflap (not shown in FIG. 6).

Flap edge fences installed on the pressure, suction or both sides of theflap airfoil attempt to alleviate the noise by increasing the distancebetween the two vortex cores. This increases the characteristictimescales associated with the unsteady vortex motion and lowers thecharacteristic frequency range away from effective perceived noise levelsensitive frequencies. Flap edge fences also alleviate the noise bymoving the vortex cores away from sharp edges and the upper surface(suction side fence) to reduce interaction associated noise. Thiseffectively results in an overall lower noise signature, especially uponapproach where airframe noise is dominant over a significant portion ofthe flyover. An additional potential benefit of flap edge fences isslightly increased lift and less induced drag resulting in a small butmeasurable increase in the lift-to-drag ratio during landing.

Fixed flap edge fences cannot be selectively stowed during cruise (anddeployed during approach). Consequently, such fixed flap edge fences mayresult in a significant pressure drag penalty due to interaction betweenthe fixed flap edge fence and local air-flow over the wing main elementas well as additional skin friction drag from the extra wetted surfacearea. In contrast, the deployable flap edge fences 406/502/602 aresuitably configured to reduce airflow noise, while minimizing additionaldrag during aircraft operations and, more specifically, during highspeed cruise. During cruise, the flap edge fence can be streamlined tominimize drag. Another, perhaps even more effective option is for theflap edge fence to be hinged, allowing it to be stowed flat against theflap surface when not deployed. For example, in an embodiment a flapedge fence in a stowed position has a smooth aerodynamic surface that isflush with the surface of the flap. Upon approach, the flap edge fencewould deploy into the position required to effectively shield the flapedge vortex from rolling over to the suction side (upper surface) of theflap. In this regard, the flap edge fence 406 may be passivelyreconfigured using the ambient temperature change with altitude, or acontrol mechanism can be utilized to actively reconfigure the flap edgefence 406 for various flight conditions.

Referring again to FIG. 4, control mechanism 416 is configured tocontrol the deployment of the flap edge fence 406 for a first set offlight conditions (such as landing and approach) to reduce the airflownoise. As mentioned above, the airflow noise is minimized by preventingthe vortex, generated at the flap side edge, from rolling over from thelower surface to the upper surface of the flap (see FIG. 1). The controlmechanism 416 also controls the stowing of the deployable flap edgefence for a second set of flight conditions (such as cruise) to minimizeextra drag by preventing the flap edge fence 406 from interacting withthe local air-flow over the wing main element 302 (See FIG. 3). Thecontrol mechanism 416 may include or be realized as a controller(connected to the aircraft systems), as explained below in the contextof FIG. 7 to facilitate changing the shape of the flap edge fence 406.

FIG. 7 is a perspective view of another example embodiment of a system700 for reducing airflow noise for an aircraft employing an activecontrol mechanism (controller). FIG. 7 illustrates a flap edge fencemodel stowed on the flap surface via an SMA torque tube employing acontroller. System 700 may have common features with system 400 such asthose described above in the context of FIG. 4. Accordingly, certainfeatures, components, and functions within system 700 that are sharedwith system 400 will not be redundantly described here. System 700includes, without limitation: a wing main element (not shown in FIG. 7),a flap 704, a reconfigurable flap edge fence 702 coupled to the flap704, a shape memory alloy (SMA) torque tube 706, and a controller 708.

A shape memory alloy (SMA) is a metal that remembers its original shapeafter being deformed from that original shape. An SMA returns to itsoriginal shape when it is heated (shape memory effect) or when thedeforming pressure is removed (superelasticity). A two-way SMA rememberstwo different shapes: one shape at a relative low temperature, andanother shape at a relative high temperature. Setting the two shapes bythermo-mechanical processing is known as “training” the SMA. An SMA withthe two shapes set is known as a “trained” SMA. The shape properties ofa trained SMA result from temperature initiated martensitic phasetransformation from a low symmetry (martensite) to a highly symmetric(austenite) crystal structure. The temperatures at which the SMA changesits structure depend on the particular alloy, and can be tuned byvarying the chemical mix and thermo-mechanical processing. Some commonSMA alloys are copper-zinc-aluminum, copper-aluminum-nickel,nickel-titanium-platinum, nickel-titanium-palladium,nickel-titanium-hafnium and nickel-titanium (NiTi or Nitinol). NiTi SMAsgenerally have superior mechanical properties to copper-based SMAs, butare also generally more expensive. Any of these, and possibly other,shape memory materials can be utilized in the various embodimentsdescribed here.

SMA torque tube 706 is coupled to the flap edge fence 702 and the flap704 (similarly, the SMA torque tube 706 may be coupled to the flap edgefence 502/602 and the flap 506/606 respectively) and is configured, asshown in FIG. 7, to shape and position the generic flap edge fence 702into a stowed position or, as shown in FIG. 8, shape and position thegeneric flap edge fence 802 (or flap edge fence 502/602) into a deployedposition, in response to a temperature change. The temperature changemay be, without limitation, the change in ambient temperature withaltitude, or a temperature change that is actively adjusted by thecontroller 708. In this regard, under a first temperature change the SMAtorque tube twists and generates a moment between the flap 704 and theflap edge fence 702 with sufficient torque to thermally deploy the flapedge fence 702 for approach and landing. Under a second temperaturechange, the SMA torque tube 706 thermally deactivates and returns to itsmartensitic shape which allows the flap edge fence 702 to stow on theflap 704 for cruise. Alternatively the austenitic and martensitic shapescan be reversed (i.e., austenitic at cruise to stow and martensitic atlanding to deploy, however this requires power). Generally, theadjustable temperate range may be about −50° C. to 25° C. For landingand approach conditions, the control temperature may be from about −10°C. to about 55° C. For cruise conditions the control temperature may befrom about −70° C. to about −40° C. The SMA torque tube may be made fromany of the materials identified above. In certain embodiments, the SMAtorque tube is formed from a material in the family of titanium-nickelalloys that have shape memory and superelastic properties. FIG. 9 showsa side view of an SMA torque tube 902. In practice, the SMA torque tube900 may be, without limitation, about 10 inches in length, about 0.25inches in diameter, and about 0.05 inches in thickness.

In practice, a lock mechanism (not shown in FIG. 8) may be employed tohold the flap edge fence 702/802 (or flap edge fence 502/602) in adeployed or a retracted position. In this regard, the flap edge fence702/802 is designed to stay stowed during take-off and cruise, anddeploy during descent before approach. A lock mechanism may be employedto maintain the stowed position until triggered by temperature oraltitude during descent. When triggered the lock releases the deployableflap, which moves to its landing configuration. On the ground thetemperature causes the flap edge fence 702/802 to change shape, stowitself, reengage the lock, and be prepared for another deployment cycle.

The controller 708 may be implemented as part of the aircraft system, acentralized aircraft processor, a subsystem computing module devoted tothe flap edge fence 704 arrangement, or the like. In operation, thecontroller 708 may control the flap edge fence 406 by monitoring thetemperature of the SMA torque tube and by heating and/or cooling the SMAtorque tube as needed. The heating/cooling of the SMA torque tube may beprovided by, without limitation, the aircraft cooling/heating systemsand the like. For example, the heater may utilize an electrical heaterelement and a controllable current source where the temperature isproportional to the current applied to the heater element. In thisregard, the controller 708 determines a temperature based on a currentflight condition, and provides heating/cooling to activate/deactivatethe SMA torque tube as explained above. This enables the controller 708to control the actuation of the flap edge fence 702 in accordance withthe current flight conditions, e.g., whether the aircraft isapproaching, landing, or in cruise. Any actuator known to those skilledin the art may be used for actuation of the flap edge fence, forexample, without limitation, a hydraulic actuator, a piezoelectricactuator, a spring loaded mechanism tied to flap and the like.

The SMA torque tube 706 is controlled based on the predetermineddeployment angle of the flap edge fence 702 as a function of temperaturecorresponding to various flight conditions. For example, the deploymentangle for landing may be, without limitation, about 90 degrees at about0° C.

In certain embodiments, the flap edge fence 406 itself is made of SMA,and it is suitably configured to bend and shape-shift in response totemperature change. The temperature change may be, without limitation,the change in ambient temperature with altitude, or a temperature changethat is actively adjusted by a controller as described in the context ofFIG. 7 above. FIG. 10 shows a perspective view that illustrates adeployed SMA flap edge fence 1006 model that is substantially parallelto the direction of the airflow 1008. FIG. 11 is a perspective view thatillustrates an SMA flap edge fence 1104 model that is thermally stowedalong the direction of streamlined air flow 1108 so that at cruiseconditions (where temperatures are relatively low) drag due to the anglebetween the direction of the streamlined airflow and the position of theSMA flap edge fence 1104 is minimized. In another configuration, an SMAflap edge fence 1104 is deployed during takeoff and landing (wheretemperatures are relatively high). Springs 1007/1106 provide a“restoring force” so that when the SMA is martensitic, the flap edgefence will move to its second shape. The springs 1007/1106 are notnecessary if the two-way SMA is employed. In this regard, the SMA flapedge fence 1104 is thermally deployed at a predetermined bending angleat a temperature range corresponding to landing and approach flightconditions. For example the bending angle may be, without limitation,about 90 degrees for landing at about 0° C. A flap edge fence 1006/1104may be of various shapes and sizes and may be mounted at variouschordwise locations near the tip of the flap as explained in context ofFIG. 4 above or on other high lift devices (such as slats).

FIG. 12 is a flowchart illustrating a process 1200 for reducing airflownoise using a deployable flap edge fence that may be performed bysystems 400-1100 as described above. Process 1200, monitors thetemperature, determines a temperature range for a specific flightcondition, and deploys or stows the flap edge fence based on thetemperature range. The various tasks performed in connection withprocess 1200 may be performed by software, hardware, firmware, or anycombination thereof. For illustrative purposes, the followingdescription of process 1200 may refer to elements mentioned above inconnection with FIGS. 4-11. In practical embodiments, portions ofprocess 1200 may be performed by different elements of system 400 andsystem 700 for reducing airflow noise, e.g., the flap, the flap edgefence, the trained SMA torque tube and the control mechanism. Process1200 is described in terms of one of the example embodiments describedherein, namely, a trained SMA torque tube to deploy the flap edge fence.

Process 1200 for reducing fluid flow noise may begin by monitoring atemperature (task 1202). Process 1200 modifies the temperature activelyby a controller connected to the aircraft systems as described in thecontext of FIG. 7 above, or alternatively may use the ambienttemperature to change the temperature of the SMA torque tube at variousflight conditions. In practice, the SMA torque tube remembers itsoriginal shape after being deformed from that original shape. In thisregard, the SMA torque tube returns to its original shape when it isheated or when the deforming pressure is removed. As mentioned above, atwo-way SMA remembers two different shapes: one shape at a relative lowtemperature, and another shape at a relative high temperature. Settingthe two shapes can be accomplished by thermal-mechanically “training”the SMA. In this regard, for example, the SMA torque tube can be trainedto remember various twisting positions corresponding to variousshapes/position of the deployable flap edge fence suitable for reducingnoise and associated drag for a range of flight conditions such ascruise and landing. These properties result from temperature initiatedmartensitic phase transformation from a low symmetry (martensite) to ahighly symmetric (austenite) crystal structure. As mentioned above, incertain embodiments, the SMA torque tube is formed from a material inthe family of titanium-nickel alloys that have shape memory andsuperelastic properties.

In this regard, if the flight condition corresponds to the cruisetemperature range (task 1204), then the temperature of the trained SMAtorque tube is changed to that of the cruise condition (task 1206), andthe trained SMA tube is thermally deactivated to return to itsmartensite shape which allows the flap edge fence to stow (task 1208) onthe flap for the cruise flight conditions. For a cruise condition, forexample, the temperature may be about −40° C.

Otherwise the method changes the temperature of the trained SMA torquetube to the temperature corresponding to the approach and landing flightconditions (task 1210), and thermally activates the SMA torque tube. Inthis regard, the SMA torque tube drives towards an austenitic trainedshape in order to generate a moment between the flap edge fence and theflap with sufficient torque to deploy the flap edge fence for theapproach and landing flight conditions. As mentioned above, in thedeployed position, the flap edge fence reduces airflow noise by reducingor preventing a vortex, generated at the flap side edge, from rollingover from the lower surface to the upper surface of the flap. As anadded benefit, lift to drag ratio during approach and landing ispotentially increased. For landing and approach conditions, for example,the temperature may be about 20 C.°, and the trained SMA torque tube maygenerate a torque in excess of 100 in-lbs to deploy the flap edge fenceby 90 degrees.

With the deployable flap edge fence as described herein, the drag due tothe flap edge fence at cruise flight conditions is minimized while theairflow noise at approach and landing flight conditions is reduced.

While at least one example embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexample embodiment or embodiments described herein are not intended tolimit the scope, applicability, or configuration of the subject matterin any way. Rather, the foregoing detailed description will providethose skilled in the art with a convenient road map for implementing thedescribed embodiment or embodiments. It should be understood thatvarious changes can be made in the function and arrangement of elementswithout departing from the scope defined by the claims, which includesknown equivalents and foreseeable equivalents at the time of filing thispatent application.

1. A system for reducing airflow noise for an aircraft having a wingmain element, the system comprising: a flap coupled to the wing mainelement; a moveable flap edge fence coupled to the flap, said flap edgefence independently moveable with respect to said flap; and a controlmechanism for the flap edge fence, the control mechanism beingconfigured to: deploy the flap edge fence by moving said flap edge fenceto a first position for a first set of flight conditions; and stow theflap edge fence by moving said flap edge fence to a second position fora second set of flight conditions.
 2. The system according to claim 1,wherein: the flap has a tip, a trailing edge, a leading edge, an uppersurface, and a lower surface; and the flap edge fence is coupled to theleading edge and to the trailing edge near the tip.
 3. The systemaccording to claim 1, wherein: the control mechanism is configured todeploy the flap edge fence into a deployed shape and position thatreduces the airflow noise by preventing rollover of vortices from alower surface of the flap to an upper surface of the flap; and thecontrol mechanism is configured to stow the flap edge fence into astowed shape and position that reduces drag by reducing interaction ofthe flap edge fence with a local air-flow over the wing main element. 4.The system according to claim 1, further comprising a trained shapememory torque tube coupled to the flap edge fence and to the flap, andconfigured to change the position of the flap edge fence in response toa temperature change.
 5. The system according to claim 4, furthercomprising a controller configured to: monitor temperature of thetrained shape memory torque tube; and provide the temperature change byheating/cooling of the trained shape memory torque tube based on aflight condition.
 6. The system according to claim 4, wherein thetemperature change is passively provided by ambient temperaturecorresponding to an altitude at a flight condition.
 7. The systemaccording to claim 4, wherein: the trained shape memory torque tube isthermally activated at a first temperature range to drive towards anaustenitic trained shape; the trained shape memory torque tube generatesa moment between the flap edge fence and the flap with sufficient torqueto deploy the flap edge fence for the first set of flight conditions;and the trained shape memory torque tube is thermally deactivated at asecond temperature range to return to its martensitic shape which allowsthe flap edge fence to stow on the flap for the second set of flightconditions.
 8. The system according to claim 4, wherein: the trainedshape memory torque tube is thermally activated to drive towards anaustenitic trained shape which allows the flap edge fence to stow on theflap, and the trained shape memory torque tube is thermally deactivatedto return to its martensitic shape which allows the flap edge fence todeploy.
 9. The system according to claim 1, wherein the flap edge fenceis made of a shape memory alloy that is configured to change shape inresponse to a temperature change.
 10. The system according to claim 9,further comprising a controller configured to: monitor temperature ofthe flap edge fence; and provide the temperature change byheating/cooling of the flap edge fence based on a flight condition. 11.The system according to claim 9, wherein the temperature change ispassively provided by ambient temperature corresponding to an altitudeat a flight condition.
 12. The system according to claim 9, wherein: theflap edge fence is thermally deployed at a predetermined bending angleat a first temperature range for the first set of flight conditions; andthe flap edge fence is thermally stowed along a direction of astreamlined air flow at a second temperature range for the second set offlight conditions.
 13. The system according to claim 1, wherein the flapedge fence is mounted to a lower surface of the flap.
 14. The systemaccording to claim 1, wherein the flap edge fence is mounted to an uppersurface of the flap.
 15. The system according to claim 1, wherein afirst flap edge fence is mounted to an upper surface of the flap and asecond flap edge fence is mounted to a lower surface of the flap.
 16. Asystem for reducing airflow noise for an aircraft having a wing mainelement, the system comprising: a flap coupled to the wing main element;a flap edge fence coupled to the flap; a trained shape memory torquetube coupled to the flap edge fence and to the flap, the trained shapememory torque tube being configured to actuate the flap edge fence inresponse to a temperature change, said actuation causing movement ofsaid flap edge fence independent of movement of said flap; and acontroller coupled to the trained shape memory torque tube, thecontroller being configured to: actively control temperature of thetrained shape memory torque tube into a first temperature range to drivethe trained shape memory torque tube towards an austenitic trainedshape, wherein the trained shape memory torque tube generates a momentbetween the flap edge fence and the flap with sufficient torque todeploy the flap edge fence for a first set of flight conditions; andactively control the temperature of the trained shape memory torque tubeinto a second temperature range to return the trained shape memorytorque tube to its martensitic shape which allows the flap edge fence tostow on the flap for a second set of flight conditions.
 17. The systemaccording to claim 16, wherein the temperature change is passivelyprovided by changes in ambient temperature.
 18. A system for reducingairflow noise for an aircraft having a wing main element, the systemcomprising: a flap coupled to the wing main element, wherein the flaphas a tip, a flap trailing edge, a flap leading edge, an upper surfaceand a lower surface; a shape memory flap edge fence coupled to the flaptrailing edge and the flap leading edge near the tip of the flap, theshape memory flap edge fence being configured to morph, in response to atemperature change, into a deployed position with a predeterminedbending angle at a first temperature range for a first set of flightconditions, and into a stowed position along a direction of astreamlined air flow at a second temperature range during a second setof flight conditions, said morphing causing movement of said flap edgefence independent of movement of said flap.
 19. The system according toclaim 18, further coin rising a controller configured to: monitortemperature of the shape memory flap edge fence; and provide thetemperature change by heating/cooling of the shape memory flap edgefence.
 20. The system according to claim 18, wherein the temperaturechange is passively provided by changes in ambient temperature.